Hi Trudi,
Cinderella's Royal Table is such an enchanting experience, your nieces are sure to love it!
I enjoy all 3 meals there, but I prefer lunch the most. They serve an entree called, "Major Domo's Pie" that is absolutely delicious. In fact, my 10 year old son begs to eat at Cinderella's Royal Table just so he can get this dish. Seriously, it's that good and is only served at lunch time.
Cinderella is always in the lobby greeting her guests. In addition, several of her Princess friends are upstairs visiting your table while you eat. Generally you will see Snow White, Jasmine, Belle and Aurora but which specific Princesses are there is subject to change.
Securing an Advanced Dining Reservation at Cinderella's Royal Table is difficult. You'll need to be online at 6am or calling 407-WDW-DINE at 7am -- exactly 180 days in advance.
Hope this helps and have a wonderful vacation,
Kaylene